javascript overhead with jitter

I am making a basic networked video player and stuffing 90% of the code into javascript, since a lot of it is string parsing and keeping track of states. It seems that playing back a movie from a matrix array in javascript introduces about a 20% cpu overhead than if I were playing it back from a jit.qt.movie object in a patch. Nothing complicated going on, just playback. Here is the basic bang function (it’s essentially taken from the javascript examples):